I'd be very curious to see how orgs like the Taxpayer's Union or Hobson's Pledge fit in. They are campaigning for our political parties but are not those parties, most of their work is not in actual campaigning but in sewing seeds of doubt or pushing certain views among the public.
I guess what the Greens are proposing is a lot better than the current state, especially the standdown between being an MP/minister and being allowed to join a lobby group.